A barrel of oil producers 1700kwh of energy..the world consumes 94 million barrels a day..94m x 1700 = 159 trillion (give or take a few hundred billion) of kWh per day.
If you need 12.8 sq metres of solar panel to produce 1700kwh..
If I divide the energy use of oil per day 159 800 000 000 divide it by 12.8.. gives me 484 375 000 sq mtrs.. or 484 375 sq kilometres.
Now I don\'t know if my maths is right. A fish rots from the head. We need more than sun light.